Jun 28, 2016 | By Alec
As the quality of 3D printers improves, the possibility of 3D printing on an extremely small scale becomes more and more realistic. While little is yet known of how 3D prints function at a micron scale, a series of experiments on 3D printed lattices by a team from the Lawrence Livermore National Laboratory (LLNL) at the Los Alamos National Laboratory revealed that 3D printing brings a lot to the table. In fact, the 3D printed micron lattices were found to exhibit unique mechanical properties that are not found in ‘disordered’ cellular materials that exist naturally.
This remarkable discovery was made by a team led by LLNL materials scientist Mukul Kumar, and also included LLNL researchers Jonathan Lind, Brian Maddox, Matthew Barham, Mark Messner and Nathan Barton, as well as James Hawreliak of Washington State University and Brian Jensen of Los Alamos National Laboratory. Their findings were just published in a paper entitled ‘Dynamic Behavior of Engineered Lattice Materials’, in the latest edition of Scientific Reports (of Nature Publishing Group).
Of course the world around us is filled with cellular structures, both manmade and natural – from bones to bridges. All these structures have a material response that is dictated by their topology, rather than by their composition. Their behavior has been extensively studied over the last few decades, as cellular materials have been recognized for their very useful thermal, electrical and optical properties. Lightweight materials are developed from the cellular structure and upwards.
To design objects with those materials, researchers typically seek to manipulate the chemistry or microstructural length scales (such as grain size distribution). But of course this approach eventually runs into certain material limitations. But with 3D printing, however, scientists can now even manipulate the architecture of the cellular material. It can be used to set up an order and periodicity at the mesoscopic scale, and as this study showed, this can embed completely new mechanical properties into the structures.
For during their experiments with these 3D printed micron structures, the researchers observed that elastic deflection of the structure occurred ahead of the compaction front. This precursor wave has not been observed in disordered materials with similar properties, such as open-cell stochastic foams which have a comparable density. “The material showed lattice characteristics in the elastic response of the material, while the compaction was consistent with a model for compression of porous media,” they say.
In fact, 3D printing imparted an elastic and compaction behavior that responds very rapidly under impact loading, giving engineers an unprecedented window of opportunity to give objects certain levels of stress resistance by 3D printing them. This paves the way for a wide number of engineering possibilities. “The basic approach is to be able to use the collective properties of an engineered structure at the micron scale to influence the macromechanical response” project lead Mukul Kumar said.
On paper, at least, 3D printing could thus usher in a whole new era when it comes to micron-scale material production. Structural engineering principles, like truss theory, can now theoretically be applied to structures at a mesoscopic scale. This means that a material’s properties could be precisely manipulated to meet application demands by 3D printing them at a micron scale. Material science might never be the same again. For more detailed information on these LLNL discoveries, check out the full research paper here.
Posted in 3D Printing Materials
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